Defective cell division leads to genomic instability;this can promote accumulation of genetic alterations required for the generation of cancer. Understanding the signaling pathways that couple the progression of the cell cycle to events required for cell division will provide insight into a key process that is required to maintain genomic stability and may provide insight for potential therapeutic targets for novel cancer treatment. The RAM (Regulation of Ace2 and Morphogenesis) network is a recently discovered signaling pathway in Saccharomyces cerevisiae that controls events that occur in late mitosis. Conserved members of the RAM network in mammalian cells regulate cell division and morphogenesis and have been associated with oncogenesis. This signaling network's function is coupled to mitotic progress, but the mechanism for this coordination is unknown. The phosphorylation state of the RAM network component Cbk1 is regulated during mitosis, and this phosphorylation may be required to maintain tight regulation of the pathway. Identification and mutagenesis of these phosphorylation sites will demonstrate their importance in RAM network regulation. Preliminary evidence suggests that the yeast polo-like kinase Cdc5 can phosphorylate Cbk1 and other RAM network components. The proposed studies will use biochemical and chemical genetic methods to explore the importance of this potential regulatory connection and examine the hypothesis that phosphorylation by Cdc5 couples the RAM network to mitosis. Determining how events required for cell division are linked to cell cycle progression will not only shed light on this poorly studied subject but may provide additional insight into potential targets for cancer treatment. Aberrant cell division can promote genetic alterations that contribute to the progression and formation of cancer. A novel signaling pathway called the RAM network controls events required for proper cell division. Examining the mechanism by which this pathway is regulated during the cell cycle may provide insight into how cells coordinate the cell cycle and cell division, and may identify novel targets for cancer treatment.